Light emitting diodes (LEDs) are a kind of semiconductor device that sends and receives a signal by converting electricity into infrared light using the characteristics of compound semiconductors or that is used as a light source.
A group III-V nitride semiconductor has been in the spotlight as the core of light emitting devices, such as light emitting diodes (LEDs) or laser diodes (LDs), due to the physical and chemical characteristics thereof.
Light emitting diodes and laser diodes do not contain environmentally hazardous substances, such as mercury (Hg), which are used in conventional lighting apparatuses, such as incandescent lamps or fluorescent lamps. Consequently, light emitting diodes and laser diodes are environmentally friendly. In addition, the light emitting diodes and the laser diodes exhibit long life spans and low power consumption. As a result, light emitting diodes or laser diodes have replaced conventional light sources.
In particular, the light emitting devices have been increasingly used in various fields, such as those of a headlamp for vehicles or a flashlight. A light emitting apparatus including light emitting devices is required to exhibit high optical extraction efficiency. In addition, demand for reduced size, weight, and cost thereof has continuously increased.
In the case in which a conventional light emitting apparatus includes a plurality of light sources, an optical system having a complicated structure is essentially required. That is, a collimating lens must be assigned to each of the light sources, and a focusing lens for collecting light beams collimated by the collimating lenses on a point is required. In general, light beams emitted from the light sources and then collimated may be spaced apart from each other by a large distance. In order to focus the light beams spaced apart from each other using a single focusing lens, it is required for the focusing lens to have a size of several tens of mm or more. If the size of the single focusing lens is increased, aberration may inevitably occur. In order to solve this problem, therefore, a prism is disposed between the collimating lenses and the focusing lens to reduce the distance between the collimated light beams. That is, in the conventional optical apparatus using the light sources, a complicated optical system, including collimating lenses, a prism, and a focusing lens, is required, whereby the structure of the optical apparatus may be complicated and the quality of a spot formed on a single point may be deteriorated.